An oil pressure transducer is often used with an internal combustion engine in an automobile to measure oil pressure and to produce a corresponding indicator signal. There have been a variety of designs for such pressure transducers many of which utilize a diaphragm, one side of which is exposed to a pressurized fluid such as the oil of the lubricating system. An design object is to provide a simple, compact yet reliable device.
Modern automobiles typically utilize a fuel injection system for the engine which includes an electric motor to power a fuel pump. In addition to the afore described oil pressure indicating function, it sometimes desirable to incorporate an electrical switch mechanism in an oil pressure transducer to control energization of the fuel pump in response to oil pressure. Specifically, it is desirable to activate the fuel pump motor only after a minimum oil pressure is reached.
A number of United States patents generally disclose a pressure transducer and switch mechanism, either singularly or in combination. For example, U.S. Pat. No. 3,321,594 to Reise discloses a fluid pressure actuated switch with a diaphragm sensor operatively associated with electrical contacts for controlling an electric fuel pump motor. The U.S. Pat. No. 4,255,630 to Hire also discloses an electrical switch which is responsive to fluid pressure to control a fuel pump motor. The U.S. Pat. No. 4,524,255 to Haag discloses a switch with a movable diaphragm responsive to fluid pressure to open and close contacts of an electrical circuit.
The U.S. Pat. No. 4,581,941 to Obermann discloses a fluid pressure transducer including a switch therein adapted to control a fuel pump motor and utilizes a diaphragm and contacts.
Several other patents have been uncovered which disclose pressure transducers without the switching device. These include U.S. Pat. Nos. 3,504,324; 4,449,112; and 4,452,202. All of the patents discussed or identified heretofore broadly disclose a pressure transducer with or without a switching mechanism but do not specifically disclose the desirable features in the fluid pressure transducer with a switching device as described hereinafter.